首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   823篇
  免费   54篇
  2023年   5篇
  2022年   19篇
  2021年   32篇
  2020年   19篇
  2019年   16篇
  2018年   16篇
  2017年   10篇
  2016年   27篇
  2015年   54篇
  2014年   52篇
  2013年   53篇
  2012年   50篇
  2011年   72篇
  2010年   43篇
  2009年   41篇
  2008年   51篇
  2007年   55篇
  2006年   42篇
  2005年   35篇
  2004年   30篇
  2003年   24篇
  2002年   21篇
  2001年   5篇
  2000年   5篇
  1999年   4篇
  1998年   4篇
  1997年   4篇
  1996年   2篇
  1995年   3篇
  1994年   3篇
  1993年   7篇
  1991年   7篇
  1990年   4篇
  1989年   4篇
  1988年   5篇
  1986年   4篇
  1985年   3篇
  1984年   2篇
  1983年   5篇
  1982年   3篇
  1981年   2篇
  1980年   4篇
  1978年   2篇
  1975年   2篇
  1974年   2篇
  1969年   3篇
  1966年   2篇
  1961年   3篇
  1960年   2篇
  1926年   1篇
排序方式: 共有877条查询结果,搜索用时 15 毫秒
101.
102.
Albania is a country of transition facing many challenges including the development and support of health and social services that will enhance the well-being of its population. Albania has one of the youngest populations in Europe and the young people face difficulties with lack of recognition and care of mental disorders, as well as violent and antisocial behaviours that may reflect violent environmental conditions and nutritional deficiencies leading to developmental problems. In this paper the behaviour of some Albanian adolescents was examined; it is probable that they are more at risk from psychological stress. For many of them the need to make a new start at a point in life at which all resources should be committed to distancing the world of childhood and starting to create a position, means a process of inevitable recession.  相似文献   
103.
Fungicides to control mycopathogens of commercial Agaricus bisporus, a mushroom cultivated for human consumption, are a major field of study, since these chemicals are toxic to both the host and its fungal parasites. The fungicide Prochloraz-Mn, used at its LD50 for A. bisporus, partially inhibited protein biosynthesis in the vegetative mycelial cell walls of this mushroom and caused significant changes in cell-wall polysaccharide structure, as deduced by methylation analysis and gas liquid chromatography-mass spectrometry (GLC-MS). Furthermore, the aggregated mycelial walls showed distinct alterations in their overall chemical composition following the administration of Prochloraz-Mn at the LD50 and the LD50 x1000. As expected, GLC-MS studies indicated that the latter dose caused more appreciable differences in polysaccharide structure. The decrease in mushroom crop yields obtained from industrial cultures treated with Prochloraz-Mn to control V. fungicola infection depended on the dose of the fungicide employed, whereas fruit-body morphology was only slightly affected at the highest Prochloraz-Mn concentration used.  相似文献   
104.
Three new dihydroxamic acids (HO(CH3)NCO-(CH2)2-CO-NH-(CH2)x-CON(CH3)OH where the x values are 4; 3 and 2, and the compounds are abbreviated as 2,4-DIHA, 2,3-DIHA and 2,2-DIHA), containing the peptide group in a certain position to one of the two functional groups and in different distances to the other one, were synthesized and their complexation with Fe(III), Mo(VI) and V(V) was studied by pH-potentiometric, spectrophotometric and in some cases by CV methods to evaluate the redox behaviour of the Fe(III) complexes and assess their potential biological activity as siderophore models. All these compounds are structural models for the natural siderophore, desferrioxamine B (DFB). The results were compared to those of the complexes of 2,5-DIHA having the same connecting chain structure and length as DFB has, and the effects of the length of the connecting chain on the co-ordination mode and on the stability of the complexes formed were evaluated.Very similar stability of the mono-chelated complexes formed with all these dihydroxamic acids was found. All the results obtained suggest that one dihydroxamic acid (even the 2,2-DIHA) is able to complete the four coordination sites of a MoO2 2+ core forming simple mononuclear complexes. Favoured monomeric structures of the bis-chelated complexes of these dihydroxamic acids are also suggested with V(V) having the smallest ionic radius among the three metal ions studied. In the case of iron(III), however, clear indication was obtained for the slightly different complexation behaviour of 2,2-DIHA. Namely, the formation of the mononuclear bis-chelated complex with this shortest ligand seems to have sufficient strain to induce the formation of bimetallic species such as [Fe(2,2-DIHA)2Fe)]2+.  相似文献   
105.
106.
107.
108.
109.

Background

Candida can be implicated in the pathology of chronic periodontitis.

Aims

To analyze the oral Candida carriage in patients suffering from chronic periodontitis (CP) and its correlation with the severity of this condition.

Methods

Microbiological samples were taken from 155 patients using the oral rinse (OR) technique and by using paper points in the periodontal pockets (GPP). These patients were divided into 3 groups: 89 patients without CP (control), 47 with moderate CP, and 19 with severe CP. Samples were cultured in a Candida chromogenic agar for Candida. Species were identified by microbiological and molecular methods.

Results

Candida was isolated in the OR of 45 (50.6%), 21 (44.7%), and 11 (57.9%) patients, respectively, and in the GPP of 32 (36%), 14 (29.2%), and 10 (42.6%) patients from the control, moderate CP and severe CP groups, respectively. Candida was isolated more frequently and in a greater burden in OR than in GPP (p < 0.01). Candida albicans was the most prevalent species. GPP of patients with CP had poor fungal biodiversity (p < 0.01).

Conclusions

Colonization by Candida was present in the samples of patients without CP, and with both moderate and severe CP. Nonetheless, patients with severe CP had a higher rate of Candida colonization, especially by C. albicans.  相似文献   
110.
We have constructed a collection of canine–rodent microcell hybrid cell lines by fusion of canine fibroblast microcell donors with immortalized rodent recipient cells. Characterization of the hybrid cell lines using a combination of fluorescencein situhybridization and PCR analysis of canine microsatellite repeat sequences allowed selection of a panel of hybrids in which most canine chromosomes are represented. Approximately 90% of genetic markers and genes that were tested could be assigned to 1 of 31 anonymous canine chromosome groups, based on common patterns of retention in the hybrid set. Many of these putative chromosome groups have now been validated by linkage analysis. This panel of cell lines provides a tool for development of genetic, physical, and comparative maps of the canine genome.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号